I think the goodbye between Sherlock and John in His Last Vow was actually a lot more moving and heartbreaking than people are giving it credit for. Especially on Sherlock's part. Because he knows he's going to his death and John doesn't.
This dialogue is so overlooked. Sherlock actually admits to being a soldier. Since the fall, he became a soldier, but does John see it? And while I've never believed Sherlock to be suicidal, I fully believe he is sacrificial. As in, he would die without a though if it would save John.